Re: [PATCH 2/3] PCI: ARM: add support for virtual PCI host controller

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On Tue, Feb 4, 2014 at 10:23 PM, Will Deacon <will.deacon@xxxxxxx> wrote:
> This patch adds support for an extremely simple virtual PCI host
> controller. The controller itself has no configuration registers, and
> has its address spaces described entirely by the device-tree (using the
> bindings described by ePAPR). This allows emulations, such as kvmtool,
> to provide a simple means for a guest Linux instance to make use of
> PCI devices.
>
> Corresponding documentation is added for the DT binding.
>
> Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
> ---
>  .../devicetree/bindings/pci/linux,pci-virt.txt     |  38 ++++
>  drivers/pci/host/Kconfig                           |   7 +
>  drivers/pci/host/Makefile                          |   1 +
>  drivers/pci/host/pci-virt.c                        | 200 +++++++++++++++++++++
>  4 files changed, 246 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pci/linux,pci-virt.txt
>  create mode 100644 drivers/pci/host/pci-virt.c
>
> diff --git a/Documentation/devicetree/bindings/pci/linux,pci-virt.txt b/Documentation/devicetree/bindings/pci/linux,pci-virt.txt
> new file mode 100644
> index 000000000000..54668a283498
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pci/linux,pci-virt.txt
> @@ -0,0 +1,38 @@
> +* ARM Basic Virtual PCI controller
> +
> +PCI emulations, such as the virtio-pci implementations found in kvmtool
> +and other para-virtualised systems, do not require driver support for
> +complexities such as regulator and clock management. In fact, the
> +controller may not even have a control interface visible to the
> +operating system, instead presenting a set of fixed windows describing a
> +subset of IO, Memory and Configuration spaces.
> +
> +Such a controller can be described purely in terms of the standardized
> +device tree bindings communicated in pci.txt:
> +
> +- compatible     : Must be "linux,pci-virt"
> +
> +- ranges         : As described in IEEE Std 1275-1994, but must provide
> +                   at least a definition of the Configuration Space plus
> +                   one or both of IO and Memory Space.
> +
> +- #address-cells : Must be 3
> +
> +- #size-cells    : Must be 2
> +
> +Configuration Space is assumed to be memory-mapped (as opposed to being

It would be great to have a flag to specify whether Configuration Space is over
ioports or memory mapped.

Regards,
Anup

> +accessed via an ioport) and laid out with a direct correspondence to the
> +geography of a PCI bus address, by concatenating the various components
> +to form a 24-bit offset:
> +
> +        cfg_offset(bus, device, function, register) =
> +                bus << 16 | device << 11 | function << 8 | register
> +
> +Interrupt mapping is exactly as described in `Open Firmware Recommended
> +Practice: Interrupt Mapping' and requires the following properties:
> +
> +- #interrupt-cells   : Must be 1
> +
> +- interrupt-map      : <see aforementioned specification>
> +
> +- interrupt-map-mask : <see aforementioned specification>
> diff --git a/drivers/pci/host/Kconfig b/drivers/pci/host/Kconfig
> index 47d46c6d8468..fd4460573b81 100644
> --- a/drivers/pci/host/Kconfig
> +++ b/drivers/pci/host/Kconfig
> @@ -33,4 +33,11 @@ config PCI_RCAR_GEN2
>           There are 3 internal PCI controllers available with a single
>           built-in EHCI/OHCI host controller present on each one.
>
> +config PCI_VIRT_HOST
> +       bool "Virtual PCI host controller"
> +       depends on ARM && OF
> +       help
> +         Say Y here if you want to support a very simple virtual PCI
> +         host controller, such as the one emulated by kvmtool.
> +
>  endmenu
> diff --git a/drivers/pci/host/Makefile b/drivers/pci/host/Makefile
> index 13fb3333aa05..9b6775d95d3b 100644
> --- a/drivers/pci/host/Makefile
> +++ b/drivers/pci/host/Makefile
> @@ -4,3 +4,4 @@ obj-$(CONFIG_PCI_IMX6) += pci-imx6.o
>  obj-$(CONFIG_PCI_MVEBU) += pci-mvebu.o
>  obj-$(CONFIG_PCI_TEGRA) += pci-tegra.o
>  obj-$(CONFIG_PCI_RCAR_GEN2) += pci-rcar-gen2.o
> +obj-$(CONFIG_PCI_VIRT_HOST) += pci-virt.o
> diff --git a/drivers/pci/host/pci-virt.c b/drivers/pci/host/pci-virt.c
> new file mode 100644
> index 000000000000..ded01474453b
> --- /dev/null
> +++ b/drivers/pci/host/pci-virt.c
> @@ -0,0 +1,200 @@
> +/*
> + * Very basic PCI host controller driver targetting virtual machines
> + * (e.g. the PCI emulation provided by kvmtool).
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + *
> + * Copyright (C) 2014 ARM Limited
> + *
> + * Author: Will Deacon <will.deacon@xxxxxxx>
> + *
> + * This driver currently supports (per instance):
> + *     - A single controller
> + *     - A single memory space and/or port space
> + *     - A memory-mapped configuration space
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/of_pci.h>
> +#include <linux/platform_device.h>
> +
> +struct virt_pci {
> +       struct device   *dev;
> +
> +       struct resource cfg;
> +       struct resource io;
> +       struct resource mem;
> +
> +       void __iomem    *cfg_base;
> +};
> +
> +static void __iomem *virt_pci_config_address(struct pci_bus *bus,
> +                                            unsigned int devfn,
> +                                            int where)
> +{
> +       struct pci_sys_data *sys = bus->sysdata;
> +       struct virt_pci *pci = sys->private_data;
> +       void __iomem *addr = pci->cfg_base;
> +
> +       /*
> +        * We construct config space addresses by simply sandwiching
> +        * together all of the PCI address components and using the
> +        * result as an offset into a 16M region.
> +        */
> +       return addr + (((u32)bus->number << 16) | (devfn << 8) | where);
> +}
> +
> +
> +static int virt_pci_config_read(struct pci_bus *bus, unsigned int devfn,
> +                               int where, int size, u32 *val)
> +{
> +       void __iomem *addr = virt_pci_config_address(bus, devfn, where);
> +
> +       switch (size) {
> +       case 1:
> +               *val = readb(addr);
> +               break;
> +       case 2:
> +               *val = readw(addr);
> +               break;
> +       default:
> +               *val = readl(addr);
> +       }
> +
> +       return PCIBIOS_SUCCESSFUL;
> +}
> +
> +static int virt_pci_config_write(struct pci_bus *bus, unsigned int devfn,
> +                                int where, int size, u32 val)
> +{
> +       void __iomem *addr = virt_pci_config_address(bus, devfn, where);
> +
> +       switch (size) {
> +       case 1:
> +               writeb(val, addr);
> +               break;
> +       case 2:
> +               writew(val, addr);
> +               break;
> +       default:
> +               writel(val, addr);
> +       }
> +
> +       return PCIBIOS_SUCCESSFUL;
> +}
> +
> +static struct pci_ops virt_pci_ops = {
> +       .read   = virt_pci_config_read,
> +       .write  = virt_pci_config_write,
> +};
> +
> +static int virt_pci_setup(int nr, struct pci_sys_data *sys)
> +{
> +       struct virt_pci *pci = sys->private_data;
> +
> +       if (resource_type(&pci->io)) {
> +               pci_add_resource(&sys->resources, &pci->io);
> +               pci_ioremap_io(nr * resource_size(&pci->io), pci->io.start);
> +       }
> +
> +       if (resource_type(&pci->mem))
> +               pci_add_resource(&sys->resources, &pci->mem);
> +
> +       pci->cfg_base = devm_ioremap_resource(pci->dev, &pci->cfg);
> +       return !IS_ERR(pci->cfg_base);
> +}
> +
> +static const struct of_device_id virt_pci_of_match[] = {
> +       { .compatible = "linux,pci-virt" },
> +       { },
> +};
> +MODULE_DEVICE_TABLE(of, virt_pci_of_match);
> +
> +static int virt_pci_probe(struct platform_device *pdev)
> +{
> +       struct hw_pci hw;
> +       struct of_pci_range range;
> +       struct of_pci_range_parser parser;
> +       struct virt_pci *pci;
> +       struct device *dev = &pdev->dev;
> +       struct device_node *np = dev->of_node;
> +
> +       if (of_pci_range_parser_init(&parser, np)) {
> +               dev_err(dev, "missing \"ranges\" property\n");
> +               return -EINVAL;
> +       }
> +
> +       pci = devm_kzalloc(dev, sizeof(*pci), GFP_KERNEL);
> +       if (!pci)
> +               return -ENOMEM;
> +
> +       pci->dev = dev;
> +       for_each_of_pci_range(&parser, &range) {
> +               u32 restype = range.flags & IORESOURCE_TYPE_BITS;
> +
> +               switch (restype) {
> +               case IORESOURCE_IO:
> +                       if (resource_type(&pci->io))
> +                               dev_warn(dev,
> +                                        "ignoring additional io resource\n");
> +                       else
> +                               of_pci_range_to_resource(&range, np, &pci->io);
> +                       break;
> +               case IORESOURCE_MEM:
> +                       if (resource_type(&pci->mem))
> +                               dev_warn(dev,
> +                                        "ignoring additional mem resource\n");
> +                       else
> +                               of_pci_range_to_resource(&range, np, &pci->mem);
> +                       break;
> +               case 0: /* cfg */
> +                       if (resource_type(&pci->cfg)) {
> +                               dev_warn(dev,
> +                                        "ignoring additional cfg resource\n");
> +                       } else {
> +                               of_pci_range_to_resource(&range, np, &pci->cfg);
> +                               pci->cfg.flags |= IORESOURCE_MEM;
> +                       }
> +                       break;
> +               default:
> +                       dev_warn(dev,
> +                               "ignoring unknown/unsupported resource type %x\n",
> +                                restype);
> +               }
> +       }
> +
> +       memset(&hw, 0, sizeof(hw));
> +       hw.nr_controllers       = 1;
> +       hw.private_data         = (void **)&pci;
> +       hw.setup                = virt_pci_setup;
> +       hw.map_irq              = of_irq_parse_and_map_pci;
> +       hw.ops                  = &virt_pci_ops;
> +       pci_common_init_dev(dev, &hw);
> +       return 0;
> +}
> +
> +static struct platform_driver virt_pci_driver = {
> +       .driver = {
> +               .name = "pci-virt",
> +               .owner = THIS_MODULE,
> +               .of_match_table = virt_pci_of_match,
> +       },
> +       .probe = virt_pci_probe,
> +};
> +module_platform_driver(virt_pci_driver);
> +
> +MODULE_DESCRIPTION("Virtual PCI host driver");
> +MODULE_AUTHOR("Will Deacon <will.deacon@xxxxxxx>");
> +MODULE_LICENSE("GPLv2");
> --
> 1.8.2.2
>
>
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